[Greenbuilding] Insulating shallow crawl spaces

John Salmen terrain at shaw.ca
Thu Apr 12 21:05:20 CDT 2012


I recommend excavating. Have done that with a few old house renovations here
as the originals were built on whatever was handy. Not as onerous as it
seems and it provides employment. Also allows you to level and take care of
any foot issues.  

 

Major concern is keeping it safe - generally not a good 02 environment
(often a sink for preservatives and poisons) so masks, suits, gloves and
ventilation are important (fresh air hoods are a good investment). 

 

From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of
elitalking
Sent: April-11-12 8:14 AM
To: Green Building
Subject: [Greenbuilding] Insulating shallow crawl spaces

 

I have a deep energy retrofit project on an old framed house where there was
no excavation for the crawls space.  The result is that the front, downhill
side of the house has adequate room for installing insulation.  However,
much of the house has less (18"-24").  The floor condition is good enough
that we are not considering removing the floor.  The room height is
insufficient to consider adding insulation to the top of the floor.  How do
I insulate the floor.  

 

For the rest of the house, we are planning on installing new ceiling rafters
parallel to the roof pitch to define 14" space to fill with open cell foam.
We are installing furring strips installed with 2" gap in front of old wood
siding.  We are adding continuous 2.5" closed cell foam to fill the gap.
The old plaster is gutted.  We can fill with adhered cellulose or open cell
foam in the 2x4 framed walls.  On another similar job, I came to the inside
of the foundation to continue closed cell foam thermal barrier and came
across the ground with closed cell foam.  All of that was covered with the
high cost spray ignition barrier.  In hind site, with that job, I would have
preferred to use rigid board insulation such as XPS.  I would create a
ground plane with combination of digging high spots and filling low spots
with crush and run (small gravel), lay one layer of extruded board to
provide puncture protection, a layer of poly for continuous vapor barrier
and another foam layer.  I put osb on top for cheap ignition barrier that
protects the foam from traffic damage.  The whole house is provided with HRV
for fresh air.  

 

However, this house does not have adequate space to work in.  

 

Do I need to hand excavate to a minimum clearance for the work? If we did
that, I could install either of the approaches describe above.   I was
wondering if I could fill the whole space with open cell foam.  I realize
that 1/2 # open cell foam is not a vapor barrier, therefore likely not a
good idea.  

 

I am encouraging my client to use a mini split heat pump to avoid the need
for ductwork in the crawl space.  Therefore, I can define the thermal
barrier at the floor plane instead of the ground.  Because we would still
have moisture issues below, I am leaning towards ground insulation.
However, a closed cell foam application to the bottom of the framing could
provide the vapor barrier to protect the wood.  Below that the stone and
concrete surfaces are not vulnerable to humidity. 

 

Right now, I consider the hand excavation to be the most likely scenario.
Because the mini split will cool the house, I am against the traditional
ventilated crawl spaces with fiberglass batts in floor framing because the
cool shadow will pull in hot humid air and cool it to dew point creating
humidity problems.    

 

This is a common situation with old house.  I hope our list can offer some
good ideas for cost affective ways of upgrading to a high standard.  

 

Eli 

www.conservationarchitect.net <http://www.conservationarchitect.net/> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20120412/4a25ca4f/attachment.html>


More information about the Greenbuilding mailing list